This invention relates to a fuel control system, and more particularly relates to a fuel control system for an internal combustion engine fuelled by a gaseous and a liquid fuel.
It is known to provide engines which operate using both a liquid and a gaseous fuel such as diesel and methane or propane; such engines are often termed "dual fuel engines".
Existing dual fuel engines are often operated on diesel only for part of the operating range of the engine and on a mixture of diesel and gaseous fuel for the rest of the operating range. In many cases the gaseous fuel flow rate is subject to very little control. Sometimes the gaseous fuel flow rate is controlled by air intake rate to the engine. In other engines a governor for the liquid fuel is used in an attempt to control the gaseous fuel flow rate.
The arrangements have never been completely satisfactory because they do not permit the control of the gaseous fuel flow rate in a way which permits optimisation of the engine performance.